Various electronic devices adopt a touch input mode which is regarded as a next-generation input technique. In this regard, many researches and developments have been actively made to provide a touch sensor capable of being applied in various environments and accurately recognizing input information by touch.
For example, since electronic devices having a touch display have been focused on an ultralight and low power thin-film flexible display having improved portability as a next-generation display, there is a need for touch sensors applicable in the display.
The flexible display is prepared on a flexible substrate that can bend, fold or roll without damage of its properties, and it may be in the form of a flexible LCD, a flexible OLED, electronic paper, etc.
In order to apply the touch input mode to such a flexible display, it needs a touch sensor having good bending, restoring, flexible and stretchable properties.
The flexible display may be prepared using a film touch sensor, for example, a wiring board comprising wiring embedded in a transparent resin substrate.
The wiring board may be prepared by a process comprising the steps of forming metal wiring on a substrate, applying and drying a transparent resin solution to cover the metal wiring and form a transparent resin substrate, and peeling the transparent resin substrate from the substrate.
For the effective peeling, organic releasing materials such as a silicon resin and a fluorine resin, and inorganic releasing materials such as a thin film of diamond-like carbon (DLC) and a thin film of zirconium oxide are pre-formed on the surface of the substrate.
However, the inorganic releasing materials may fail to effectively peel the metal wiring and the resin substrate from the surface of the substrate on which a part of the metal wiring and the resin substrate may be remained, while the organic releasing material may be come out from the surface of the metal wiring and the resin substrate.
That is, it is difficult to induce perfect peeling of the metal wiring from the substrate despite of using the releasing materials.
Korean Patent No. 10-1191865 discloses a method for preparing a flexible substrate having metal wiring embedded therein, comprising forming a sacrificial layer, metal wiring and a polymer material on a substrate and removing the sacrificial layer by a solvent or light to peel the metal wiring and the polymer material from the substrate.
The removal of the sacrificial layer according to the above method is, however, difficult to be carried out in a large size, and various base films are difficult to be used in the above method which cannot be implemented in a high temperature condition.